treewide: initialize empty structs with var

Change-Id: I72d3993eaf5fe57c77b1dda8218e36a8cc11813d
Reviewed-on: https://review.monogon.dev/c/monogon/+/3108
Tested-by: Jenkins CI
Reviewed-by: Serge Bazanski <serge@monogon.tech>
diff --git a/metropolis/node/core/consensus/testhelpers.go b/metropolis/node/core/consensus/testhelpers.go
index 8b0b213..3522e06 100644
--- a/metropolis/node/core/consensus/testhelpers.go
+++ b/metropolis/node/core/consensus/testhelpers.go
@@ -25,7 +25,7 @@
 func TestServiceHandle(t *testing.T, cl *clientv3.Client) ServiceHandle {
 	ca := pkiCA()
 
-	tsh := testServiceHandle{}
+	var tsh testServiceHandle
 	st := &Status{
 		cl:                        cl,
 		ca:                        ca,